C4牧草饲用成分在植株中的分布规律及其适宜刈割高度

Feed Nutrients Distribution Pattern in Different Parts of C4 Forages and Their Suitable Cutting Heights

在收获期将高丹草(Sorghum bicolor×Sorghum sudanese)、玉米(Zea mays)和象草(Pennisetum purpureum)3种C 4禾本科牧草不同节位的茎秆、叶片和叶鞘分离,分别测定其粗蛋白(CP)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、非结构性碳水化合物(NSC)含量以及干物质体外消化率(IVDMD)等饲用品质性状。结果表明:玉米IVDMD和CP含量最高,显著高于高丹草和象草(P<0.05);玉米和高丹草的NSC含量显著高于象草(P<0.05);象草NDF和ADF含量最高,玉米的最低。玉米叶片CP含量高于茎秆和叶鞘,但象草和高丹草茎秆CP含量显著高于叶片和叶鞘(P<0.05);象草CP含量随着节位的降低逐渐升高,高丹草则相反。3种C 4牧草不同节位叶鞘和叶片中可溶性碳水化合物(WSC)含量极显著低于茎秆(P<0.01),其中高丹草茎秆WSC含量显著高于玉米(P<0.05),象草的最低;高丹草倒3~4节茎秆中的WSC含量最高,倒9~10节显著降低;玉米倒3节后茎秆中的WSC含量逐节升高,倒8~10节最高;象草茎秆WSC含量呈现V字形变化,倒1~4节逐节下降,随后逐节升高,倒11节最高。因此收获玉米应降低留茬高度,而高丹草和象草适宜刈割高度分别为倒8节和倒11节。

At harvest stage,the contents of nonstructural carbohydrates(NSC),crude protein(CP),neutral detergent fiber(NDF),acid detergent fiber(ADF),and in vitro dry matter digestibility(IVDMD)of stem,leaf and sheath were measured in different internodes of maize(Zea mays),elephant grass(Pennisetum purpureum)and sorghum-sudan hybrid(Sorghum bicolor×Sorghum Sudanese).The results showed that the IVDMD and CP content of maize was higher than those of sorghum-sudan hybrid grass and elephant grass(P<0.05);the content of NSC in maize and sorghum-sudan hybrid grass was higher than that of elephant grass(P<0.05);the content of NDF and ADF was the highest in elephant grass,and lowest in maize.The CP content in maize leaf was higher than that in stem and sheath(P<0.05),but the CP content in the stem of elephant grass and sorghum-sudan hybrid grass was much higher than that in leaf and sheath(P<0.05);the CP content in elephant grass increased with the decrease of node position,while the content of CP in sorghum-sudan hybrid grass decreased with the reduction of node position.The content of water soluble carbohydrates(WSC)in the stem of three forage grasses was significantly higher than that in sheath and leaf(P<0.01),and the WSC content in sorghum-sudan hybrid grass stem was significantly higher than that of maize stem(P<0.05),in which the WSC content in elephant grass was the lowest;the content of WSC in the top 3^rd~4^th node of sorghum-sudan hybrid grass was the highest;the content of WSC in maize stem increased after top 3 rd node with the decrease of node positions;the WSC content in elephant grass stem showed“V”pattern,which decreased from the top 1^st~4^th nodes,and then increased from the top 8^th10^th nodes,in which the top 11^th node had the highest value.In conclusion,the cutting height in maize can be reduced as much as possible,while for the suitable cutting height in sorghum-sudan hybrid grass and elephant grass is about from the top 8^th and 11^th node,respectively.